Jet propulsion had long been a dream amongst aircraft engineers and designers in many countries, and experiments were going on in several European countries as well as the United States during the 1920s and 1930s. The greatest obstacle to development during this period lay in the absence of suitable metals for the turbine blades capable of standing up to the stresses of this revolutionary type of engine. Designers were experimenting with ram-jets, rockets and pulselets as well as the turbine power plant which is now such a familiar part of the world aviation scene.
Ernst Heinkel in Germany was one of those who were convinced that the figure of 800 km/h (500 mph) represented the peak that could be achieved by propeller-driven aircraft particularly because the thrust of an airscrew decreases with increased flight speed. In 1935 he wrote an article on this subject which went on to explore the possibilities of jet propulsion with special reference to the turbo-jet. In the same year he met Wernher von Braun who was destined to become world famous as the father of the American space programme. Von Braun was at that time testing a primitive rocket engine fuelled with methyl alcohol and liquid oxygen. He had already tested his motor units by building a turntable on which he fixed several power units which turned it at considerable speed before they disintegrated. Von Braun was convinced that the power units had the potential to power an aircraft and succeeded in persuading an interested Ernst Heinkel to provide an aircraft fuselage for further ground tests.(1)
Early experiments resulted in the total destruction of the first three He 112 airframes which Heinkel provided, but early in 1937 the fourth He 112 took off using its conventional Junkers Jumo 210 engine with the Von Braun rocket engine installed in the rear of the fuselage. After levelling off, the pilot, Erich Warsitz, ignited the rocket motor and flew for the first time under rocket propulsion. The short flight ended in an emergency landing without undercarriage extension, as the cockpit filled with fumes and gases and the aircraft burst into flames causing severe damage. Nevertheless the first flight powered by thrust instead of a propeller had been made.(2)
From these early experiments the limitations of rocket motors became apparent; their thrust was to a great extent uncontrollable and their fuel was of a dangerous and unstable nature and its consumption was so high that engine power was only available for a matter of minutes on each flight. However, the enormous power that could be generated instantly led to the further development of the rocket motor as assistance in take-off for heavily laden aircraft and for small airfield operations. This opened up a whole new field in aircraft technology.
Heinkel then proposed that he should design an aircraft specifically for the rocket motor and the He 176 was built under conditions of extreme secrecy. Tailored round the 1.9 m frame of test pilot Erich Warsitz, the aircraft was kept as small as possible - both length and wingspan being approximately four metres. It incorporated a jettisonable cockpit capsule for the safety of the pilot - the forerunner of the modern ejector seat.(3)
June 1939 saw ground testing in progress and on the morning of 30 June, Heinkel was awoken by an ecstatic Warsitz announcing the first ever pure rocket flight lasting just over 50 seconds. On the following day the He 176 was demonstrated to Generals Udet and Milch and two days later to Chancellor Adolf Hitler, Generalfeldmarschall Goëring and many senior officers.(4)
Meanwhile, work on the first turbo-jet engines had reached an advanced stage and a prototype of Heinkel's HeS 3 engine, designed by the young engineer Pabst von Ohain, was installed in the tail of a Heinkel 118 dive bomber whilst retaining the conventional engine in the nose. Day after day in the early dawn the secret tests of the jet turbine went on using the piston engine for take-off until one day the turbine engine burnt out on landing. Heinkel now felt once again that a purpose-built airframe was needed and the He 178 was designed and built around the second prototype HeS 3 engine. During ground tests on 24 August 1939 the aircraft lifted off the runway for a few yards and three days later it made the first circular flight and landed safely although the undercarriage refused to retract in flight.(5)
The Heinkel He 178 thus became the first aircraft in the world to fly by turbo-jet propulsion, preceding Britain's Gloster-Whittle G40 by some 21 months.(6)
Further test flights continued and on 1 November 1939 the aircraft was successfully demonstrated to a sceptical group of Luftwaffe officers, including Generals Milch and Udet, despite a delay caused by a faulty fuel pump which Heinkel astutely covered up by giving his guests a lengthy champagne breakfast at the factory club.(7)
The development of German jet engines had been going on since 1935 as purely private ventures in the factories of Heinkel and of the Junkers airframe company until 1939 when government support was offered to existing piston-engine manufacturers if they would undertake the development of jet turbine engines.(8)
Junkers were pressured by the Air Ministry to transfer their gas turbine development work from their airframe company to their engine company in June 1939. As a result of this their best engine designer, Max Mueller, left Junkers with most of his staff and went to work with Heinkel taking some of his designs with him.(9)
Heinkel continued the development of the Ohain designs in parallel with Mueller's engine and acquired the Hirth Motoren engine works in Stuttgart to accommodate the second design team and its product.(10)
Meanwhile both the Brandenburgische Motorenwerke (Bramo) and Bayerische Motorenwerke (BMW) companies were working on their own engines and Bramo were absorbed by BMW in mid-1939. Daimler-Benz were lukewarm about the jet turbine project preferring to concentrate on their conventional engine production but yielded to official pressuie to investigate the process. They designed an engine designated 109-007 but made no real effort to bring it to a developed state and the project was allowed to fall away in 1943.(11)
With the successful flights of the He 178 behind him, Heinkel was aware of the design problems of the single-engined jet fighter with the engine in the fuselage and decided to turn his attention to a twin-engined aircraft whose engines could be suspended under the wings. His new design designated He 280 went on to the drawing boards in the summer of 1939 and the prototype airframe was completed a year later. The HeS 8A turbo-jet engines for which it was designed were not ready so the airframe was completed as a glider with dummy engine nacelles and made a number of test flights in this configuration. The jet engines were installed early in 1941 and on 5 April the first jet-powered flight of the He 280 took place. Apart from its engine installations, the He 280 also broke new ground with its unconventional tricycle undercarriage which was viewed with much suspicion by the German aviation authorities.(12)
Eight prototypes were constructed and were fitted with a variety of engines including the Junkers Jumo 004 and BMW 003 turbo-jets. However, it was symptomatic of the in-fighting that took place throughout the German aircraft industry and air ministry from the 1930s onwards, that the He 280 project was shelved in favour of the Messerschmitt Me 262 although Heinkel was a full year ahead of Messerschmitt in the development of his aircraft. Instead Heinkel's engine design team were forced to work on a type of turbo-jet, the oblique-flow compressor, which was extremely difficult to manufacture and took so long to develop that only a prototype was ready for bench tests by the end of the war and the whole effort of Heinkel's jet engine team was wasted.(13)
Heinkel's greatest contribution was the He 162 Volksja"ger single seat fighter which went from drawing-board to flight test in some 90 days. Designed round the BMW 003 engine (of which an example is on display at the SA National Museum of Military History) it was intended as a 'last ditch' defensive aircraft to be flown by relatively untrained personnel in the final defence of the Reich. A number of aircraft were delivered to the Luftwaffe in January 1945 for proving flights and training but there are no reported incidents of them being actually flown in combat situations. This was the first in-service aircraft to be equipped with an ejector seat.(14)
The Messerschmitt Me 262 was the first operational jet aircraft to enter frontline service on either side in World War II. The design work was started in 1939 and the first airframes were produced in 1941 at which time the development of the jet engines was still in progress. The first flight took place in April 1941 with a single Junkers Jumo 210 G 12-cylinder piston engine driving a propeller and centrally fitted in the nose of the aircraft.(15)
The first flight with jet engines from Bayerische Motorenwerke (BMW) was undertaken in March 1942 when the nose-mounted piston engine was fortunately retained as the thrust from the wing-mounted turbo-jets proved inadequate to get the machine airborne and only the use of the piston engine enabled the test pilot to bring his aircraft safely back to the airfield.(16)
Jumo 004 A engines were then installed and the next test flight took place in July 1942 without the piston engine.(17)
The aircraft had been designed as a fighter, but in January 1944 Hitler decided that it should be used as a fast intruder bomber with the particular aim of attacking the Allied forces when they eventually attempted the inevitable invasion of Europe. Due to the very slow development of the engines, aircraft production commenced only in April 1944 and that with an engine that was far from having all its development problems solved. Initial small quantities of the aircraft began to be delivered to the Luftwaffe for flight testing and training purposes in July 1944 and several experimental armament variations were designed and tested. The need for a trainer aircraft for the conversion of pilots to this unusual and difficult type produced the first two-seater versions where the rear fuel tank was removed to provide seating for a second pilot, equipped with a full set of controls. One of these aircraft, further modified for use as a night fighter, is on show at the Museum and a two-seat trainer aircraft may be seen at the Naval Air Station at Willow Grove in the United States of America.(18)
The first fighter sorties of the Me 262 were flown from the end of July 1944 and the bomber version followed in August. However, the bomber was not a success due to the very small bomb load carried and the difficulties of good bomb-aiming from a very fast aircraft. This version was soon dropped in favour of further development as a fighter especially for night interception. In this role the Me 262 was successful in combat against the Allied air forces and the hitherto inviolate Mosquitos were frequently attacked and brought down. The heaviest losses amongst the Me 262s came from technical failures and pilot-originated crashes rather than from enemy action.(19)
In the Autumn of 1940, Arado Flugzeugwerke began studies on the production of a medium-range reconnaissance aircraft designed around the new turbo-jet engines then under development by Junkers and BMW. The planned power of these engines was expected to produce performances in altitude and speed that would allow the aircraft to operate without escorts or armament and could thus permit the design of a small, light-weight airframe.(20)
The resultant design designated Arado Ar 234 was a single-seat shoulder-wing monoplane with two turbo-jet engines slung under the wings. The required range of 2 150 km (1340 miles) necessitated a small fuselage cross section and maximum fuel capacity both of which precluded the fitting of a conventional undercarriage especially in view of the extreme length of the legs that would have been required due to the height of the wing off the ground. Arado therefore designed a take-off trolley which could be jettisoned at the moment of lift-off leaving the aircraft to land on small retractable skids.(21)
Whilst two prototype airframes were ready for testing as early as the end of 1941, the long delays in engine development held up the initial flight and this only took place on 30 July 1943 and early flights revealed problems with the take-off trolley. This was to preclude the carriage of bombs under engines or fuselage and the Air Ministry ordered further prototypes to be fitted with a tricycle undercarriage, whilst flight testing continued using several trolley-equipped prototypes and experimental rocket pods to assist in short airfield take-offs. It was the first production aircraft in the world to carry, as standard equipment, a braking parachute to shorten its landing run.(22)
The Ar 234 was designed as a photo-reconnaissance aircraft and a small test unit - Kommando Goelz - was established with two trolley-equipped aircraft and commenced training. Following urgent demands from the High Command for accurate reconnaissance information on the advancing Allied forces in Normandy, Leutnant Erich Sommer, the second pilot of the Kommando, took off on 2 August 1944, and flew three long photographic runs over the Normandy beach-heads without interference achieving more in one flight than all the German reconnaissance units in the West had done in the previous two months.(23)
Once the aircraft had been re-designed to incorporate a conventional tricycle undercarriage, a small number were produced but the quantity was restricted by the shortage of Jumo 004 engines which were mainly allocated to the Messerschmitt Me 262 production. Whilst photo-reconnaissance remained its main function, a number were successfully used as bombers and a few converted for night fighting although there is no record of these achieving any success. A radar operator was carried on the night fighters to operate the FuG 218 NEPTUN airborne interception set and two 20 mm cannon were mounted under the fuselage.(24)
Arado were experimenting with a four engined version designated Ar 234 C which was designed to use the less powerful BMW 003 engine, but this aircraft had only reached the prototype stage at the end of hostilities. An Ar 234 B was captured on the ground on 25 February 1945 by the advancing American 9th Army at Segalsdorf and taken back to the USA for evaluation, providing the Allies with their first complete example of a German combat jet aircraft.(25)
Junkers designed and built a prototype of their Ju 287, a four-seat heavy bomber, but the factory fell into Russian hands before flight tests could be completed and two prototypes were taken to Russia with many of the German production team and was subsequently flown there in 1947/48.(26)
Henschel's Hs 132A was a single-seat dive bomber with the unique feature that the pilot lay in a prone position in the aircraft. Only prototypes were built before the factory was overrun by the advancing Soviet forces.(27)
Apart from their Me 262 series, Messerschmitt were working on what was the most advanced jet fighter concept, the P 1101, a variable geometry or 'swing-wing' aircraft which never proceeded beyond the construction of a prototype and which was scheduled to begin flight testing in June 1945. The work was being carried out at a secret research establishment at Oberammergau which was discovered accidentally by the advancing US forces on 29 April 1945. Immediate evaluation of the plant was undertaken by a Combined Advanced Field Team which, by chance, was led by Robert J Woods, chief designer and co-founder of the Bell Aircraft Corporation who immediately started work on completing the prototype. Unfortunately, the technical specifications had been hidden some distance away from Oberammergan and these fell into the hands of French troops who sent them to Paris for evaluation where the authorities declined to release them to the Americans. The prototype was crated and sent back to the USA and later became an important source of information to the Bell Company in the development of swing wing aircraft.(28)
The last German jet aircraft contender was the Gothaer Wagonfabrik whose heavy bombers of World War I were considered such a serious threat that a special clause was inserted into the Versailles treaty specifying the complete destruction of their aircraft-manufacturing division. Between the wars their activities were almost exclusively in the field of light aircraft and gliders together with the building of other companies' aircraft on contract. During World War II they built over 3 000 Messerschmitt Me 110 fighter bombers. Between the wars they had conducted many experiments in tailless aircraft similar to the famous Pterodactyl aircraft designed by Professor G T R Hill in Britain and this led to their involvement with the Horten brothers who had been designing and developing 'flying wing' gliders since 1931. Later designs were fitted with small engines driving pusher airscrews and their work was encouraged by the German authorities after both brothers joined the Luftwaffe in 1936. More powered versions of their 'flying wing' were built and in 1943, despite the lack of official interest, they went on with the construction of their first prototype for the development of their jet-powered flying wing fighter. They were fortunate in capturing the interest of Reichsmarschall Go~ring with this totally unauthorized prototype and he gave his backing to the whole project. Flight tests of the prototype commenced in January 1945, but the first aircraft was destroyed in a crash in March, killing its pilot after only two hours of flight time had been achieved and, whilst several others were built covering different versions of the aircraft, no further progress was made before the factory was overrun by the Allied forces.(29)
Messerschmitt Me 163 rocket-powered fighters were first reported in action on 28 July 1944 by North American P51 Mustangs of the US 359th Fighter Group, which were escorting a Boeing B-17 Flying Fortress formation on a daylight attack on Merseburg and subsequently Me 163s were regularly reported in action over Germany although with very limited success. By the end of 1944 little use was being made of them due to the Allied advances and the critical shortage of rocket fuel. A prototype of an advanced version, the Me 263 with a retractable undercarriage was built but never put into production. Prototype Me 163s were also built under licence in Japan, despite the loss of the U-boat carrying the sample aircraft and the full manufacturing specifications which was sunk whilst on its way to Japan. No combat record exists of the Japanese version.(30)
In a class by themselves were the various rocket-powered aircraft developed by the Germans including the Fieseler Fi 103 Vergeltungswaffe Fins (Reprisal Weapon One) better known as the 'Flying Bomb' which was also produced in a manned version designated Reichenberg IV. Bachem's Ba 349A Natter flew successfully but never saw action whilst DFS (German Research Institute for Gliding) was testing a prototype high-altitude reconnaissance aircraft DFS 228 which was to be carried aloft on top of a Dornier Do 217 bomber.(31)
To power the Flying Bomb, a new form of engine had been developed which might be described as a combination of jet and rocket propulsion. This was the Argus As 014 pulse jet or intermittent propulsive duct. Messerschmitt designed their Me 328 as a small, single seat, expendable fighter-bomber to be powered by two of these engines. Several prototypes were constructed and test flown and experiments were conducted with a detachable 'dolly' type undercarriage, catapult take-off, carriage aloft and towing behind Dornier Do 217 bombers. The greatest problem that was never overcome was the considerable vibration caused by the pulse jets which led to many instances of damage to the aircraft structure and the eventual abandonment of the project.(32)
In all, Germany produced around 200 designs using either pure jet propulsion, rockets or a mixture of piston and jet engines.
Of these David Masters quotes the following analysis:
Three pure jets and two rocket propelled aircraft actually delivered to the Luftwaffe for operational service -
Ar 234, Me 262, He 162, Ba 249 and Me 163.
A further 25 jet and rocket types in flight test status.
Six or so in the process of being built.
Some two dozen had reached an advanced stage of design before being either abandoned or overtaken by events. Approximately 150 designs never got beyond the drawing board.(33)
In summation, the German aircraft industry produced a great many ideas for jet propelled aircraft. The majority of these were overtaken by time and the advancing Allies, and did not get beyond die drawing board or model stages. However, it is extremely doubtful if most of these would ever have achieved production status or contributed in any way to the war effort. Their designs were largely impracticable, and lacked the potential for the further development which is essential to the life of a combat aircraft. The German aircraft industry was fortunate in having several companies actively engaged in research into jet propulsion, and because of this both the Soviet and United States authorities made very strenuous efforts to obtain the services of their technicians at the end of hostilities.
1. E. Heinkel, He 1000, (London, Hutchinson, 1950), pp. 237-258.
2. Ibid., p. 242.
5. Ibid., pp. 242-245.
4. Ibid., p. 247.
5. Ibid., p. 252.
6. W. Green & R. Cross, The Jet Aircraft of the World, (London, MacDonald, 1955), pp. 40-42.
7. E. Heinkel, op. cit., p. 255.
8. W. Green & R. Cross, op. cit., p. 11.
9. Ibid., p. 12.
E. Heinkel, op. cit., pp. 257-258.
10. Ibid., p. 261.
11. W. Green & R. Cross, op. cit., p. 15.
12. E. Heinkel, op. cit., pp. 259-266.
15. Ibid., p. 265.
W. Green, Warplanes of the Third Reich, (London, MacDonald, 1970), p. 561.
14. E. Heinkel, op. cit., p. 269.
15. J. Ethell & A. Price, The German Jets in Combat, (London, MacDonald & Jane's, 1977), p. 11;
W. Green, op. cit., p. 620.
18. J Ethell & A. Price, op. cit., p. 15.
A Pritchard Messerschmitt, (New York, Putnam, 1975), pp. 158-162.
19. Ibid p 164
W Green op. cit., pp. 627-654.
20. J Ethell & A. Price, op. cit., p. 74.
21. Ibid p 75.
22. Ibid pp 74-80.
25. Ibid pp 80-81.
W. Green, op. cit., p. 53.
24. J. Ethell & A. Price, op. cit., p. 98.
25. W. Green, op. cit., pp. 54-56.
26. Ibid., pp. 495-495.
27. Ibid., p. 405.
28. A. Pritchard, op. cit., p. 169.
29. W. Green, op. cit., pp. 246-251.
30. A. Pritchard, op. cit., pp. 155-147.
31. Ibid., pp. 64-172.
32. Ibid., pp. 656-658.
A. Pritchard, op. cit., pp. 166-168.
33. D. Masters, German Jet Genesis, (London, Jane's, 1982). p. 9.
Bridgman, L (ed.) Jane's All the World's Aircraft 1945/46. (Newton Abbott. David & Charles Reprints. 1970.)
Brown, E. Wings of the Lüftwaffe. (London. MacDonald & Jane's. 1977.)
Ethell, J & Price, A. The German Jets in Combat. (London. MacDonald & Jane's. 1979.)
Green, W. Warplanes of the Third Reich. (London. MacDonald. 1970.)
Green, W & Cross, R. The Jet Aircraft of the World. (London. MacDonald. 1955.)
Heinkel, E. He 1000. (London. Hutchinson. 1956.)
Masters, D. German Jet Genesis. (London. Jane's. 1982.)
Pritchard, A. Messerschmitt. (New York. Putnam. 1975.)
Turner, P. Heinkel - an album. (Shepperton. Allen. 1970.)
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